1.去掉下列各式中的括号.
(1) (a-b)-(c-d)=________;
(2)(a+b)-(-c+d)=_______;
(3)-(a+b)+(c-d)=________;
(4)(a+b)-3(c-d)=_______.
2.3ab+b2+_______=4ab-b2.
3.-2a+1的相反数是_______.
4.多项式3x2—5x-7与6x2—5x-2的和等于_______;差等于_______.
5.已知a、b、c三数在数轴上的位置如图所示,
化简 _______
二、选择题
6.下列去括号错误的是 ( )
A.2x2-(x-3y)=2x2-x+3y B. x2+(3y2-2xy)= x2+2xy-3y2
C.a2+(-a+1)=a2-a+1 D.-(b-2a)-(-a2+b2)=b+2a+a2-b2
7.化简m+n-(m-n)的结果为 ( )
A.2m B.-2m C.2n D.-2n
8.代数式-[a-(b-c)]去括号应为 ( )
A.-a-b+c B.-a+b-c C.-a+b+c D.-a-b-c
9.下列运算正确的是 ( )
A.-3(x-1)=-3x-1 B.-3(x-1)=-3x+1
C.-3(x-1)=-3x-3 D.-3(x-1)=-3x+3